Secure integrated circuits (ICs) are widely used in secure systems. Some example secure systems are banking payment terminals, personal identification number (PIN) entry devices, smartcard readers, and security tokens. Often, sensitive information (e.g., PINs to banking accounts, social security numbers, or cryptographic keys) is stored and/or manipulated in the secure ICs. This sensitive information needs to be protected against attackers who attempt to access the information by physically breaking through the packaging of secure ICs by chemical or other means.
To protect sensitive information, some conventional secure ICs are included in ball grid array (BGA) packages, which have ball connectors located under the packages. The ability of a hacker to physically probe an IC package can be reduced by using ball connectors instead of conventional IC pins, because the ball connectors are not located on the edge of the package and thus cannot be probed as easily as IC pins. A plastic cap located on top of the IC package can help prevent a hacker from probing from the top of the IC package. However, in some scenarios, the plastic cap can be opened by chemical means, allowing secure information to be accessed by probing bonding wires or by manipulating a physical surface of a semiconductor die exposed after a portion of the plastic cap has been removed.